Fujitsu VRF II units

[steevec]

Hi,

i've just completed an installation of 17 systems of Fujitsu V-II series.
They range over most outdoor models available and are combination of single, double and triple outdoor unit sytems.
All are operating normally. however.....When operating on gen set and the mains power comes back on. Some will not reset and go into error locking out.
This is random and not always the same systems . There could be 1 or 4 locking out with the others fine.
I have managed to get the gen set/electrical contractor to increase the time interval for the changeover to 15 seconds.
This seems to be the time taken to loose all power on the control board. This seems to cure most of the problem most of the time.
But we still have the odd trip. Fujitsu say they have not experienced this problem in any other pacific island countries where these operate. So am wondering what could be causing this and if it is voltage related could I install iron ring toriod for example on the 240v feed onto the control board. The voltages go through filter boards and all sorts of cleaning devices so really would appreciate some feedback if anyone has experienced this.
I do not want to go to the costly expense of installing contactors and timers etc to give it a longer time out.If you turned the isolator off and then back on after a few seconds you also get this trip.I cannot figure why it can happen on one changeover and not the next on any given system.

[flyinkiwi]

Try progressively longer delays - hopefully you find a solution by allowing time for all caps to discharge.

Is transfer switching performed at zero crossing?

Could you delay powering up your outdoor units, and stagger their connection to the supply AFTER transfer switch is engaged and power supply is stable?

My suspicion would be around instantaneous voltage dips if everything is connected simultaneously, made worse if the whole network is being re-energised at the same time.

[steevec]

Thanks,
Yes I will check on the power and zero crossing
The error it comes up with suggests it is picking up a phase issue. So I was wondering if the protection devices are sensing power not quite in sync.

But at the end of the day once the boards loose power then the changeover seems to go okay.
The only way I see to stagger the start up is to put in contactors and timers etc which won't be cheap.

I'm confused by the fact that no one around the PI's, NZ and Aussie from Fujitsu's comments have every heard or experienced this. (Those that are on Gensets because most gen set transfers back to main is fairly quick.) The outdoor units start after a 3 min or so time delay once power is on but the error occurs immediately once power is restored if before the cap discharge.So voltage dips I don't believe are a factor. Changing the transfer time seems to get them going but doesn't address the real issue. I'll have to try and persuade the electrician to lengthen the transfer time.
Would you know of a relatively inexpensive way to stagger the outdoor start up apart frpm timers and contactors on each unit. Fujitsu whilst very good are not overly interested as they do not see it as there issue.
Thanks
Steve

[Brian_UK]

I may be thinking this all wrong but...

What would happen if you could switch the units OFF (not the power, just the control circuit) at the reinstatement of the power supply? This would perhaps bring in the normal system restart mode as against trying to keep the units running during changeover.

[flyinkiwi]

I may be thinking this all wrong but...

What would happen if you could switch the units OFF (not the power, just the control circuit) at the reinstatement of the power supply? This would perhaps bring in the normal system restart mode as against trying to keep the units running during changeover.

I think that might create more issues with restarting controllers - but there may be some merit in it, if the indoor units or outdoor units have a digital input to utilize for that purpose. Otherwise, powering everything down and back up will result in the controller restarting with its previous settings.

At any rate, it sounds like a good idea from the point of view of not shutting down a running machine at every change over.

It seems very much akin to a Daikin U4 fault.

Steve, have you spoken to Dave at Fujitsu in Welly? He has the best knowledge of Fujitsu faults. Next to me, that is. Tell him I said that.

Otherwise, timers and contactors would be the only solution I can think of.

Shame you didn't mention it sooner - was in Suva in October.

Edit: A timer will set you back maximum $125 + GST, and a 50A contactor or 3ph SSR about $440 + GST, NZD, so I guess the cost over 17 units may add up. Group them in lots of 3-5 units to cut the cost of your timers down. Not a huge saving, but "Every little helps."